Motorized machine electrical system arc detection apparatus and methods

ABSTRACT

Disclosed is a motorized machine which includes an electrical system monitoring system which results in detecting arcing in the electrical distribution system of the machine and the ability to provide notification and protection for such arcing. The system functions to monitor the electrical distribution system of the machine to sense the frequencies of signals in the system using appropriate filtering. One type of filtering which may be used is based upon a heterodyning circuit which provides variable frequency filtering for filtering a signal representative of the current in at least one electrical circuit of the machine. The heterodyning circuit output is configured to produce a signal which may be logarithmically related to the filtered signal. If the output signal exceeds a predetermined limit (representative of noise) for a predetermined period (representative of a typical arc duration), the system generates an arc signal. The arc signal may then be used to operate a circuit interrupter or an indicator in a circuit protection system or both.

FIELD OF THE INVENTION

[0001] The present invention relates, in general, to arc fault detectionand, more specifically, to arc fault detection in an electricaldistribution system of a motorized machine.

BACKGROUND OF THE INVENTION

[0002] There are various conditions that may cause an arc fault.Corroded, worn or aged wiring or insulation, insufficient contactpressure, electrical stress from repeated overloading, etc., may resultin an arc fault. These conditions may damage the insulation of thewiring and create excessive heating temperatures. In general, theseconditions have been found to occur in applications where vibrations andrelatively high temperatures are normally present. More specifically,vehicles (e.g. automobiles, airplanes, trucks, off-road equipment, etc.)and other moving or vibrating equipment provide a harsh environment forelectronics and electrical systems (direct current (D.C.) or alternatingcurrent (A.C.)).

[0003] The development of electronics and electrically poweredaccessories has resulted in an increase in the use of electronics andelectrical power in vehicles. Examples of electronics and electricallypowered accessories used in vehicles include:

[0004] electronic fuel injection or fuel control;

[0005] electronic timing control;

[0006] electronic transmission shift control;

[0007] electronic HVAC control;

[0008] electronic lighting control;

[0009] electronic braking control (e.g. anti-lock braking, tractioncontrol, slip control, etc.);

[0010] power convenience accessories (e.g. power seats, power windows,heated seats, personal lighting, heated steering wheels, power sun roof,power steering wheel tilt, power mirrors, tire inflation control, etc.);

[0011] electronic cruise control;

[0012] on-aboard navigation systems; and

[0013] air bags.

[0014] Many of the electronics and power accessories listed above arealso used in aircraft and off-road vehicles (e.g. tractors, trackedvehicles, excavators, etc.). With hybrid and pure electric vehicles, theuse and transmission of electrical power is multiples greater than withconventional vehicles due to the use of electricity to power the motorswhich propel the vehicles.

[0015] As a result of the substantial increase in use of electronics andelectrical power accessories in vehicles, and the use of electric motorsto propel vehicles, the potential for arc faults in the electricalsystems of vehicles has also increased. As discussed above, such arcingcan damage wiring and electronics or, cause unwanted heating. Thus, itwould be desirable to provide a system for detecting and controlling arcfaults in vehicle electrical systems.

[0016] Detection and control of arc faults is relatively complicated.For example, the occurrence of an arc fault in one branch circuit of apower distribution system of a vehicle may generate a false arcdetection signal in another branch circuit. As a result, circuitbreakers or interrupters in more than one branch circuit may erroneouslytrip. Relatively noisy loads within the vehicle, such as electric motors(engine fan, heater fan, power seat motors, etc.) can create highfrequency disturbances, which may appear to be arc faults and causeunwanted circuit breaker tripping. Similarly, external high frequencydisturbances within the machines' operative environment also may appearto be arc faults and cause unwanted circuit tripping.

[0017] There are two types of arc faults that may occur in a vehicle. Afirst type is a high-energy arc that may be related to high currentfaults; a second type is a low current arc that may be related to theformation of a carbonized path between conductors. The first type mayresult from an inadvertent connection between a line conductor andneutral conductor or a line conductor and ground. The first type maydraw current that is above the rated capacity of the circuit, arcing asthe conductors are physically joined.

[0018] The other type of arc fault, the carbonization between electricalconductors, may be considered more problematic. Since the current in thearc may be limited to less than the trip rating of an associated circuitbreaker or interrupter, such arcs may become persistent withoutobservation and may result in certain conditions. Contact arcs may becaused by springs in switches that become worn which, in turn, mayreduce the forces that hold electrical contacts together. As theelectrical contacts heat and cool down, the conductors may touch andseparate repeatedly, thereby possibly creating arcs known as “sputteringarcs.” Such sputtering arcs can create carbonized paths resulting inpersistent low current arcs in the electrical system.

[0019] Contact arcs or sputtering arcs may also be observed in contactswhich are made from different materials. For example, aluminum wiringwhich contacts copper wiring may oxidize at the contact points. In thiscase a non-conductive layer may build up over time between the contactpoints and arcing may result.

[0020] In view of the potential for arc faults in vehicles, it would bedesirable to provide vehicles with arc fault detection.

SUMMARY OF THE INVENTION

[0021] The present invention provides a motorized machine whichgenerates vibration during operation. The machine includes a motorconfigured to generate mechanical energy, a source of electrical energy,at least one electrical load having a function, an electricaldistribution system configured to couple the electrical load to thesource of electrical energy, and a circuit protection system coupled tothe electrical distribution system. The circuit protection system isconfigured to interrupt application of electrical energy from the sourceof electrical energy or to indicate an arc event in response to an arcsignal. An electrical arc detection circuit is coupled to the circuitprotection system and is configured to monitor the electrical energy andgenerate the arc signal when the electrical energy generates a signalrepresentative of an electrical arc.

[0022] Another embodiment of the invention provides a method fordetecting an arcing fault in a motorized machine that generatesvibration, with the motorized machine having an electrical distributionsystem including a circuit protection system, a source of electricenergy, and at least one electrical load having a function. The methodof arc detection comprises the steps of monitoring the electricaldistribution system with a superheterodyne circuit, generating anoscillator frequency which cycles between a low frequency and a highfrequency. The oscillator circuit is coupled to the superheterodynecircuit. Eliminating background and spurious noise with a comparatorcircuit coupled to the superheterodyne circuit in a reference voltageterminal. Monitoring time of the arcing fault based on a signal from thecomparator circuit with an arc timing monitor circuit. Compensating forarcing drop-outs based on signal from the arc timing monitor circuitwith a compensating circuit. Generating a further signal indicative ofthe arc fault if the predetermined time period if exceeded with anaccumulating circuit based on the signal from the compensating circuitand, generating an arc signal to operate the circuit protection system,with the trip signal generation circuit based on further signal from theaccumulating circuit. Another embodiment of the method of arc detectionincludes the step of activating one of a circuit interrupter and anindicator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a block diagram representation of a vehicle including anembodiment of an arc detection circuit.

[0024]FIG. 2 is a detailed circuit diagram of an exemplary embodiment ofan arc detection circuit.

[0025]FIG. 3 is a detailed circuit diagram of a simulated arc generationcircuit.

[0026]FIG. 4 is a detailed circuit diagram of an exemplary embodiment ofa DC arc detection circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027]FIG. 1 is a block diagram representation of a vehicle or a machine10 whether land, air or sea based. Vehicle 10 includes a D.C. energystorage power source 12 (e.g., a battery), an A.C. or D.C. power source14 (e.g. a generator or alternator driven by engine 16, a fuel cell, ora photovoltaic device such as a solar cell array), a motor engine 16,engine controls 18, heating, ventilating and air conditioning system 20(HVAC), lighting 22, traction and braking system controls 24, a brakingsystem 26, an application function control A 28, and an applicationspecific function control B 30. If the vehicle is a land based vehiclesuch as an automobile, truck or off-road machine equipment (e.g.tractor, excavator, tracked vehicle or construction equipment), thevehicle could also include electronic transmission controls 32, atransmission 34, and typically at least one driven wheel 36 and mayinclude an implement 37. The implement 37 can be, for example, a spindlecoupled to the motor 16 for spinning a material against a tool forshaping the material, or a movable arm coupled to the motor 16 to movematerials in a predetermined manner such as a crane or a backhoe.

[0028] In general, in land based vehicle 10, motor engine 16 ismechanically coupled to transmission 34 which is mechanically coupled toat least one drive wheel 36. In operation the mechanical energy fromengine 16 is transmitted through transmission 34 which controls thedirection and speed of wheel 36 relative to engine speed 16. In mostmodern vehicles such as automobiles, engine 16 is controlled byelectronic engine controls 18. Such controls 18 typically controlelectronic fuel injection, electronic timing and, in some cases,electronic engine valves. In most modern vehicles such as automobiles,high powered tractors and off-road equipment, electronic transmissioncontrols 32 control the shifting of transmission 34 based uponparameters such as engine speed signals from electronic engine control18, and signals from the electronic braking and traction control systems24.

[0029] The HVAC system 20 typically includes temperature controls andair movement fans. Lighting system 22 typically includes the vehiclelighting and the appropriate lighting controls which vary substantiallyfrom vehicle to vehicle. More specifically, in addition to the primaryvehicle lighting provided to permit vehicle operation in the dark, manyvehicles include interior lighting systems for instruments andcompartment lighting.

[0030] Referring to traction and braking system controls 24, thesecontrols are coupled to the braking system 26 and, as discussed brieflyabove, to transmission control 32. Traction control systems aregenerally known and operate to pulse the brakes on various wheels of avehicle to redirect power flow through the vehicle differentials tolimit the application of power to a wheel spinning at a rate highrelative to the other powered wheel(s) of the vehicle. The brakingsystem control in most modern vehicles is commonly referred to as anantilock braking system and operates to relieve pressure on the brakeswhen the system determines that the wheel associated with a particularbrake is sliding relative to the surface upon which the vehicle istraveling.

[0031]FIG. 1 includes two application function controls 28 and 30.However, depending upon on the vehicle or machine, this number may vary.One example of an application specific function control would be theelectronics and control system for an onboard navigation system 38.Another example of an application specific function control would be thecontrol for the vehicle air bags 40. Other examples of systems which mayrequire applications specific function controls include power seats,power windows, heated seats, personal lighting, heated steering wheels,power sun roofs, power steering wheel tilt, power mirrors, tireinflation control, off-road vehicle slip control, electronic cruisecontrol, etc.

[0032] In vehicles and machines, including substantial numbers of theelectronic controls and electrically powered accessories such as thosediscussed above, all of these controls require power from a power sourcesuch as D.C. power source 12 which in most vehicles and machines is astorage battery which in turn today is charged by A.C. power source 14,that is typically an alternator and appropriate voltage regulator andrectification system. Alternatively, a D.C. generator can be used tocharge the battery. As vehicle electronics and wiring systems becomemore complicated, a range of circuit protection 42 is provided. Manycircuits in vehicles are currently protected by passive circuitprotection such as fuses which are responsive to a very limited type ofcircuit fault. These limited types of circuit fault are short circuitand overload.

[0033] One of the problems with having a limited range of circuitprotection is the absence of protection for circuits when arcing isoccurring within the electrical system. Such arcing can create noisewithin the system which can interfere with sensitive electronics and,more dangerously, can create fire within the vehicle. Accordingly,circuit protection 42 includes a circuit interrupter 48, such as forexample, controllable mechanical or semiconductor circuit interruptersand fuses for interrupting the application of D.C. power to the vehicleelectronics. In particular, power source 12 is coupled to enginecontrols 18, transmission control 32, HVAC system 20, lighting 22,traction control and braking system controls 24, application specificfunction control A 28 and application specific function control B 30with circuit protection system 42. In operation, circuit protectionsystem 42 can interrupt power supplied to the various electronics viaelectrical distribution system 41 power conductors 18A, 32A, 20A, 22A,24A, 28A and 30A.

[0034] In some applications, the circuit protection system 42 includesan indicator 49 that enunciates an arcing event in the one or morespecific functions in the vehicle electronic system. Specific functions,such as electronic braking or window motors, should not have powercut-off, notwithstanding arcing. In such instances when the arcdetection circuit 44 detects an arcing event, an arc signal is sent tothe circuit protection system 42 which in turn activates the indicator49. The indicator 49 can be a visual display that may comprise a warninglight, an audible signal, including a message, tone or noise or atactile indicator such as a vibrating surface in contact with the systemoperator. The indicator 49 can be located within the vicinity of theoperator of the vehicle 10 or machine having the arc detection circuit44 to alert the operator to the arcing event with the operator thentaking appropriate action. Thus, at the option of the arc detectionsystem designer, the circuit protection system 42 can be configured toenunciate an arcing event, interrupt electrical power-supply or both.

[0035] To protect against arcing within the vehicle electronic system anarc detection circuit 44 is provided. In particular, an arc detectioncircuit 44 is configured to detect signals generated within one or moreconductors 18A, 32A, 20A, 22A, 24A, 28A or 30A which are representativeof arcing within the electrical circuits, electronics and electricalequipment associated with these circuits. In simpler systems, arcdetection circuit 44 may only monitor the power conductor from source12. Of course, the specific monitoring scheme can be varied dependingupon cost constraints, detection accuracy requirements, reliabilityrequirements, etc.

[0036] In operation, arc detection circuit 44 monitors the conductors todetermine if arcing is present. If an arcing event is present, circuit44 provides an arc signal to the circuit protection system 42 alongsignal conductor 46 to activate an indicator 49 to notify the systemoperator, or the circuit interrupter 48, which then will trip one ormore of the circuit breakers or circuit interrupters associated with theconductors to provide power from power source 12 to the respectivecontrols and electrical equipment or both. Signal conductor 46 mayinclude one or more signal conductors depending upon a number ofconductors being monitored for arcing.

[0037] Depending upon the vehicle and electronics being provided power,circuit protection system 42 may include indicators 49 and circuitinterrupters 48 such as electronically controlled circuit breakers orappropriate semiconductor switches which can be controlled (opened orclosed) based upon a signal from arc detection circuit 44.

[0038] Vehicle 10 was described above as a land based vehicle. However,vehicle 10 could be any other type of vehicle including an airplane,jet, boat, etc. Depending upon the type of vehicle, the engine may be apiston engine or turbine engine and may be fueled by gasoline, dieselfuel, natural gas, etc. In the case of an airplane or jet, vehicle 10would not include a transmission 34 or transmission controls 32. Rather,propulsion of the vehicle would be generated directly from turbine(s) orpropeller(s) coupled to the engine(s) 16.

[0039] The use of vehicle electronics and electrically poweredcomponents has increased and continues to increase in vehicles. Theseincreases in vehicle electronics has resulted in substantial rises incurrents in conventional automotive powered systems which have typicallya range of 12-14 volts. As a result, it is likely that battery voltageswill be increased to voltages above 12 volts (e.g. range of 36 volts to42 volts nominal). Currently, most over-the-road semi-trucks include 24volt systems and aircraft include AC voltage systems for example nominal24 volts AC. These increased voltages will also increase the potentialfor arcing due to the fact that increased voltages permit arcing tooccur over larger air gaps.

[0040] Notwithstanding the range of voltages mentioned, the detectiontechniques described herein are not voltage sensitive. The technique forAC circuits applies for all AC voltages and likewise, the technique forDC circuits applies to all DC voltages.

[0041] Referring now to FIG. 2, FIG. 2 is a detailed circuit diagram ofarc detection circuit 44. In general, arc detection circuit 44 includesan oscillator 50, a heterodyning chip 52 such as chip number SA626manufactured by Phillips Semiconductor, a power source 54, a levelcomparator circuit 56, and arc time monitoring circuit 58, one shotcircuit 60, a time accumulating circuit 62, and a trip signal generationcircuit 64. Oscillator 50 is coupled to the oscillator inputs OSE-E andOSC-B of heterodyning chip 52. In general, oscillator 50 is configuredto generate an oscillator frequency which cycles between a low frequencyand a high frequency. Ideally, this frequency range would be as broad aspossible if it were not cost and component restrained. Some applicationsmay permit costs which would support a range of 20.0 to 40.0 megahertz,and the circuitry shown in FIG. 2 provides an oscillator which generatesoscillator frequencies which cycle from 30.0 to 35.0 megahertz whereinthe oscillator cycles from the low to the high oscillator frequency inless than one millisecond.

[0042] Power supply 54 is a D.C. power supply which supplies three (3)volts to circuit 52 as shown in FIG. 2. This power supply is connectedto the D.C. power source 12, but could be configured for connection toA.C. power source 14.

[0043] Circuit 52 monitors an electrical circuit (i.e. voltage orcurrent) at the RF_(in) and RF_(out) pins. Depending upon theapplication these pins are coupled to the positive and/or negativeconductors in the circuit. The particular configuration shown in FIG. 2is for connection to an A.C. system with the conductors of the systembeing connected at RF_(in) and RF_(out) of chip 52. Chip 52 is alsocoupled as shown to two 10.7 megahertz filters 80 and 82. These filterswere selected based upon the frequencies which are permitted for RFcircuit use by the U.S. Government. However, depending upon futureavailability or uses for the circuit, these filters may be changed tofilter at other center frequencies. Chip 52 is wired as shown in FIG. 2so that chip 52 operates to subtract the frequency of the signal inputat RF_(in) and RF_(out) from the frequency of oscillator 50, and filterthe difference in these frequencies at 10.7 megahertz. The result isthat circuit 52 provides a variable frequency filter.

[0044] An analysis of arcing in both A.C. and D.C. circuits shows thatarcing generates relatively high amplitude signals across a very largerange of frequencies including at least 20.0 through 40.0 megahertz.Accordingly, since oscillator 50 oscillates between 30.0 and 35.0megahertz, chip 52 will generate a continuously high signal at the RSSIoutput throughout the oscillation of oscillator 50 when arcing isoccurring in the system coupled to the RF input 51 of chip 52. However,when chip 52 merely detects signals which exist at selected frequenciesbetween 30.0 and 35.0 megahertz, chip 52 will only generate spikes orpulses at the RSSI outputs.

[0045] Circuit 52 provides logarithymic amplification to the filtereddifference between the oscillator 50 signal and the signal applied toRF_(in) and RF_(out).By way of example, this signal generated at RSSI isset to be within a range of 0 to 1 volts wherein that voltage is anindication of the decibel level of the input signal RF_(in).

[0046] The signal at RSSI is applied to comparator circuit 56. Circuit56 includes a comparator 66 and reference voltage terminals 68. Inoperation, comparator circuit 56 changes output state (e.g. goes high)only if a voltage generated by circuit 52 exceeds the predeterminedvoltage reference set at terminal 68. The purpose of comparator circuit56 is to eliminate the effects of background and spurious noise on arcdetection. If the signal generated at the RSSI output is greater thanthe reference signal 68 the output of comparator 66 is set high (i.e.changes state from the normal state representative of no arcing to astate representative of arcing). The signal at the output of comparator66 is applied to time monitoring circuit 58.

[0047] Time monitoring circuit 58 operates to determine if the time theoutput of comparator 66 is high is indicative of the time period (e.g.milliseconds or more) of a typical arcing event. If the time period issufficient, then time monitoring circuit 58 applies a signal to one shotcircuit 60 which compensates for the extinguishing of an arc when thevoltage of the monitored A.C. power goes through the zero crossing. Thepurpose of the mono-stable multi-vibrator circuit (60) also generallyknown as a one-shot circuit, is to count the number of arcinghalf-cycles in an AC wave form.

[0048] The signal from one shot circuit 60 is applied to accumulatingcircuit 62 which determines if there has been arcing for at least apredetermined number of half cycles (e.g. three) of the A.C. systembeing monitored for arcing. If arcing exists for a predetermined numberof half cycles, a signal is applied by circuit 62 to trip circuit 64which outputs a trip signal on conductor 46 to operate a circuitinterrupter such as a circuit breaker or provide a signal to operate anindicator 49.

[0049] The components of the vehicle described in reference to FIG. 1would normally require D.C. electrical power. The detection circuit ofFIG. 2 is configured for an A.C. system and is readily converted intoarc detection circuit for a D.C. electrical system. In particular, toconvert the circuit of FIG. 2 to an arc detection circuit for a D.C.electrical system, a 1.0 k resistor 141 is inserted at the output ofcomparator 66, and capacitor 150 and diode 156 of one-shot circuit 60are removed and replaced by a direct connection between the output ofcomparator 146 and the negative input of comparator 164. The threeassociated resistors 152, 154, and 158 of one shot circuit 60 areremoved as well as resistor 148. It should be understood that “removed”as used herein may mean simply disconnecting the appropriate lead in thecircuit. An exemplary embodiment of a DC circuit is illustrated in FIG.4. The purpose of this change is to compensate the lack of zerocrossings in D.C. circuits. Arcing drop outs compensated for typicallyhave variable durations, for example 0.5 millisecond or 1.0 millisecond.

[0050] To monitor the desired electrical circuit either currenttransformers (CT) or shunts can be used as appropriate to couple the RFinputs of chip 52 to the circuit to be monitored. Depending upon theapplication and type of loads on electrical circuits either a CT orshunt and the respective configuration thereof would be chosen. Forexample, for A.C. and D.C. applications it is desirable to eliminatefundamental A.C. or D.C. current signals. Since the frequency range ofinterest for the circuit shown in FIG. 2 is between 30.0 and 35.0megahertz, the core of a CT would be a low permeability core. Such lowpermeability core provides relatively good immunity from noise signalsin the kilohertz range.

[0051] Referring to FIG. 3, FIG. 3 illustrates a test circuit 70including a contact switch having contacts 72 and an output terminal 74which is coupled to ground wherein the conductor 76 from transistor 78passes through the system CT. In operation, when contacts 72 are broughtinto contact, circuit 70 generates a signal which simulates arcingthrough conductor 76 which is then monitored by the current transformerassociated with the A.C. arc detection circuit of FIG. 2 or the D.C. arcdetection circuit of FIG. 4 discussed above.

[0052] The following is a table listing all of the components set out inFIGS. 2, 3 and 4 and their associated reference numbers, component typesand values or part references as applicable. Component Value orReference No. Component Type Part Reference 52 Heterodyning SA626Circuit 66 Comparator LM2901 78 Transistor 2N3904 80 10.7 MH_(z) FilterSFECA10.7MAS 82 10.7 MH_(z) Filter SFECA10.7MAS 84 Capacitor 0.1 μF 86Resistor 5.49 k ohms 88 Resistor 3.74 k ohms 90 Comparator LM 2904 92Resistor 66.5 k ohms 94 Resistor 22.1 k ohms 96 Resistor 33.2 k ohms 98Capacitor 0.074 μF 100 Operational LM2904 Amplifier 102 Resistor 51 kohms 104 Diode MV 7005 106 Capacitor 68 pF 108 Capacitor 39 pF 110Inductor 33 nH 112 Capacitor 39 pF 114 Resistor 22.1 k ohms 116Capacitor 39 pF 118 Capacitor 1000 pF 120 Capacitor 1000 pF 122Capacitor 1000 pF 124 Capacitor 1000 pF 126 Capacitor 1000 pF 128Capacitor 0.1 μF 130 Resistor 4.99 k ohms 132 Resistor 4.02 k ohms 136Resistor 2.3 k ohms 138 Resistor 86.6 k ohms 140 Capacitor 0.033 μF 141Resistor 1.0 k ohms 142 Resistor 11.3 k ohms 144 Resistor 33.2 k ohms146 Operational LM2901 Amplifier 148 Resistor 20 k ohms 150 Capacitor.01 μF 152 Resistor 60 k ohms 154 Resistor 60 k ohms 156 Diode 1N4148158 Resistor 60 k ohms 160 Resistor 5 k ohms 162 Resistor 20 k ohms 164Operational LM2901 Amplifier 166 Resistor 20 k ohms 168 Transistor2N3904 170 Resistor 42 k ohms 172 Resistor 9 k ohms 174 Capacitor 0.1 μF176 Resistor 150k ohms 178 Resistor 150k ohms 180 Resistor 20 k ohms 182Transistor 2N3904 184 Resistor 10 k ohms 186 Operational LM2901Amplifier 188 Resistor 20 k ohms 190 Capacitor 0.01 μF 192 Resistor 10 kohms 194 Transistor 2N3904 196 Resistor 8 k ohms 198 Resistor 10 k ohms200 Capacitor 0.01 μF 202 SCR EC103D 204 Capacitor 0.1 μF 206 VoltageRegulator LM317 208 Resistor 20 k ohms 210 Resistor 150 k ohms 212Resistor 48 k ohms 214 Resistor 10 k ohms 216 Transistor 2N3904 218Resistor 1 k ohms 219 Capacitor 0.1 μF 220 Capacitor 0.01 μF 222Transistor 2N3904 224 Transistor 2N3904 226 Resistor 68 k ohms 228Resistor 510 k ohms 230 Capacitor 1.2 nF 232 Transistor 2N3904

[0053] While two embodiments and multiple applications for the arcdetection system have been disclosed and described in detail, variousother modifications could be considered within the scope of theinvention. For example, it is contemplated that the A.C. or D.C. arcdetection would be usable in vibrating equipment such as machine tools,robots, and other manufacturing equipment. By way of another example,the center filter frequency of 10.7 megahertz may be modified dependingupon frequencies made available by the Government in the future and theparticular application for the arc detection. Furthermore, dependingupon component availability and cost the frequency range and cyclingfrequency of oscillator circuit 50 may be modified to suit particularapplications, cost constraints and component availability. Stillfurthermore, it is contemplated that all or a portion of the circuitrydisclosed may be embodied on a single chip, and further modificationsmay include multiple channels of arc detection. These modifications andother applications are intended to be covered in the scope of theappended claims.

What is claimed is:
 1. A motorized machine which generates vibrationduring operation, the machine comprising: a motor configured to generatemechanical energy; a source of electrical energy; at least oneelectrical load having a function, wherein the load requires electricalenergy to accomplish the function; an electrical distribution systemconfigured to couple the electrical load to the source of electricalenergy; a circuit protection system coupled to the electricaldistribution system; and, an electrical arc detection circuit coupled tothe circuit protection system and configured to monitor the electricalenergy and generate an arc signal when the electrical energy generates asignal representative of an electrical arc.
 2. The machine of claim 1,further comprising an electrical conductor of the electricaldistribution system which couples to the electrical load to the sourceof electrical energy, and the detection circuit includes a currenttransformer coupled to the electrical conductor.
 3. The machine of claim2, wherein the electrical detection system includes: a superheterodynecircuit configured to monitor the electrical distribution system; anoscillator circuit configured to generate an oscillator frequency whichcycles between a low frequency and a high frequency, with the oscillatorcircuit coupled to the superheterodyne circuit; a comparator circuitconfigured to eliminate background and spurious noise, the comparatorcircuit coupled to the superheterodyne circuit and a reference voltageterminal; an arc timing monitor circuit configured to monitor time ofthe arcing fault based on signal from the comparator circuit; acompensating circuit configured to compensate for arcing drop outs whensignal from the arc timing monitor circuit is received by thecompensating circuit; an accumulating circuit configured to receive thesignal from the compensating circuit and generate a further signalindicative of the arc fault if a predetermined time period is exceeded;and, a trip signal generation circuit configured to receive the furthersignal from the accumulating circuit and generate an arc signal tooperate the circuit protection system.
 4. The machine of claim 3,wherein the circuit protection system includes one of a circuitinterrupter and an indicator.
 5. The machine of claim 4, wherein thecircuit protection system is configured to interrupt application ofelectrical energy from at least one of the electrical storage device andthe electrical power source in response to the arc signal.
 6. Themachine of claim 4, wherein the circuit protection system is configuredto signal an arcing event with one of a group including, a display, alight, an audible message, an audible tone, an audible noise and atactile indicator.
 7. The machine of claim 2, wherein the electricalload requires electrical energy provided at a relatively constantvoltage.
 8. The machine of claim 4, further comprising a spindle coupledto the motor for spinning a material against a tool for shaping thematerial.
 9. The machine of claim 4, further comprising a movable armcoupled to the motor to move materials in a predetermined manner. 10.The machine of claim 4, further comprising at least one wheel coupled tothe motor to move the machine.
 11. A method for detecting an arcingfault in a motorized machine that generates vibration, with themotorized machine have an electrical distribution system including acircuit protection system, a source of electrical energy, and at leastone electrical load having a function, the method of arc detectioncomprising the steps of: monitoring the electrical distribution systemwith a superheterodyne circuit; generating an oscillator frequency whichcycles between a low frequency and a high frequency, with an oscillatorcircuit coupled to the superheterodyne circuit; eliminating backgroundand spurious noise with a comparator circuit coupled to thesuperheterodyne circuit and a reference voltage terminal; monitoringtime of the arcing fault based on a signal from the comparator circuitwith an arc timing monitor circuit; compensating for arcing drop outsbased on signal from the arc timing monitor circuit with a compensatingcircuit; generating a further signal indicative of the arc fault if apredetermined time period is exceeded, with an accumulating circuitbased on the signal from the compensating circuit; and, generating anarc signal to operate the circuit protection system, with a trip signalgeneration circuit based on the further signal from the accumulatingcircuit.
 12. The method of arc detection of claim 11, including the stepof coupling a first filter to the superheterodyne circuit.
 13. Themethod of arc detection of claim 12, including the step of coupling asecond filter to the superheterodyne circuit.
 14. The method of arcdetection of claim 13 wherein each filter is configured to operate at afrequency of 10.7 megahertz.
 15. The method of arc detection of claim14, including the step of installing the arc detection circuit in avehicle.
 16. The method of arc detection of claim 11, including the stepof activating one of a circuit interrupter and an indicator.
 17. Themethod of arc detection of claim 16, wherein the circuit protectionsystem is configured to interrupt application of electrical energy fromat least one of the electrical storage device and the electrical powersource in response to the arc signal.
 18. The method of arc detection ofclaim 16, wherein the circuit protection system is configured to signalan arcing event with one of a group including, a display, a light, anaudible message, an audible tone, an audible noise and a tactileindicator.
 19. The method of arc detection of claim 11, including thestep of coupling an implement to the motorized machine.
 20. The methodof arc detection of claim 19, wherein the implement is selected from agroup including: a spindle, a movable arm and a wheel.